Distributed data access systems are known that require a central authority responsible for defining a rigid set of conventions, known as a global schema, to control the way in which data is structured and represented at the various sites that make up the system. The existence of the global schema restricts the autonomy of the local sites and results in rigidity and delay with regard to when and how data is stored and accessed.
A simple database system which may be accessed remotely is described in GB 1581136, which describes an information handling system and terminal apparatus. Information may be displayed as an index and selections may be made by operators by operation of a keypad to indicate which item of a displayed index is required.
The system effectively describes an arrangement of linked flat pages where a selection made on the top level page will result in a lower level page being supplied to a user.
The database structure of this type only allows pre-stored information to be supplied to users.
The present invention is directed towards the problem of accessing central relational database systems, where database specific commands are required to be activated in response to local selections. These types of commands may involve complex filtering combining and displaying commands so as to derive optimum benefit from relational databases containing a plurality of tables. In the aforesaid known system, no provision is made for activating commands of this type, given that all data supplied to users is predefined. Such an arrangement would therefore have serious limitations when access is to be provided to relational databases.
When users are given direct access to relational databases, highly sophisticated commands, usually defined using Standard Query Language (SQL) may be directed at the database. These may cause undesirable operations to be effected upon the database which may corrupt data or, more likely, may consume significant amounts of processing time as re-indexing operations are performed. It is therefore desirable to provide the power of relational database environments while at the same time providing a level of restriction upon the extent to which some users may be given access to certain procedural systems.